The flowers of this plant are frequented by various insects, chiefly by bees, for the sake of the pollen. Hermann Muller, however, has shown (‘Die Befruchtung’ etc. page 277) that V. nigrum secretes minute drops of nectar. The arrangement of the reproductive organs, though not at all complex, favours cross-fertilisation; and even distinct species are often crossed, for a greater number of naturally produced hybrids have been observed in this genus than in almost any other. (3/9. I have given a striking case of a large number of such hybrids between Verbascum thapsus and lychnitis found growing wild: ‘Journal of Linnean Society Botany’ volume 10 page 451.) Nevertheless the present species is perfectly self-fertile, if insects are excluded; for a plant protected by a net was as thickly loaded with fine capsules as the surrounding uncovered plants. Verbascum lychnitis is rather less self-fertile, for some protected plants did not yield quite so many capsules as the adjoining uncovered plants. Plants of Verbascum thapsus had been raised for a distinct purpose from self-fertilised seeds; and some flowers on these plants were again self-fertilised, yielding seed of the second self-fertilised generation; and other flowers were crossed with pollen from a distinct plant. The seeds thus produced were sown on the opposite sides of four large pots. They germinated, however, so irregularly (the crossed seedlings generally coming up first) that I was able to save only six pairs of equal age. These when in full flower were measured, as in Table 3/25. TABLE 3/25. Verbascum thapsus. Heights of Plants measured in inches. Column 1: Number (Name) of Pot. Column 2: Crossed Plants. Column 3: Self-fertilised Plants of the Second Generation. Pot 1 : 76 : 53 4/8. Pot 2 : 54 : 66. Pot 3 : 62 : 75. Pot 3 : 60 5/8 : 30 4/8. Pot 4 : 73 : 62. Pot 4 : 66 4/8 : 52. Total : 392.13 : 339.00. We here see that two of the self-fertilised plants exceed in height their crossed opponents. Nevertheless the average height of the six crossed plants is 65.34 inches, and that of the six self-fertilised plants 56.5 inches; or as 100 to 86. Vandellia nummularifolia.